Three dimensional conical horn antenna coupled image detector and the manufacturing method thereof

ABSTRACT

The present invention relates to three dimensional conical horn antenna coupled image detectors and the manufacturing method thereof. More specifically, the present invention relates to the method of manufacturing an image detector by coupling three dimensional conical horn antenna with the image detector which are constructed using the Micro Electro Mechanical System (MEMS) Technology that improves the sensitivity of the image detector.

BACKGROUND OF THE INVENTION

The present invention relates to three dimensional conical horn antennacoupled image detectors and the manufacturing method thereof. Morespecifically, the present invention relates to the method ofmanufacturing an image detector by coupling three dimensional conicalhorn antenna with the image detector which are constructed using theMicro Electro Mechanical System (MEMS) Technology that improves thesensitivity of the image detector.

The conventional method of improving the performance of an imagedetector has normally been relied on the coupling two dimensionalantenna with the image detector.

As illustrated in FIG. 1 a and FIG. 1 b, the configuration diagram of anconventional conical horn antenna coupled image detector shows that theimage detector 3 is located within the waveguide 5 of the conical hornantenna constructed on the substrate 1. The shape of the image detector3 is a square type.

However, some of the problems of the conventional configuration forimage detectors are as follows;

Firstly, the coupling of two dimensional antenna results a significantincrease in the size of image detectors causing difficulties in an arraytype manufacturing.

Secondly, the conventional image detectors are not effective forcoupling with conical horn antenna due to their square shape.

Thirdly, the floating structure of the conventional image detectors forthermal isolation could cause a serious damage to the structure duringthe coupling with antenna.

Fourthly, the loss of light receiving part of the conventional antennacoupled image detectors becomes large because the thermal isolation legsas well as absorption layer are included in the antenna simultaneously.

SUMMARY OF THE INVENTION

The present invention is designed to overcome the above problems ofprior arts. The object of the invention is to provide an image detectorthat can effectively couple with conical horn antenna using the MEMStechnology. Another object is to provide the manufacturing method of animage detector which is coupled with three dimensional conical hornantenna.

In order to achieve the stated objectives, the present invention mainlyfocuses on the manufacturing process technology of the support whichsupports the conical horn antenna, the circular absorption layer whichhas the identical diameter to that of a bottom cross section of thewaveguide of the antenna and the circular shaped thermal isolation leg.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 a and FIG. 1 b, are configuration diagrams of an conventionalconical horn antenna coupled image detector.

From FIG. 2 to FIG. 4 represent the basic configuration diagram, singleisolated configuration diagram and a cross section of the image detectorcoupled with conical horn antenna array according to the presentinvention.

FIG. 5 a and FIG. 5 b show an overall configuration of the conical hornantenna and the simulation results of its directivity respectively.

FIG. 6 a and FIG. 6 b show an overall configuration of the square hornantenna and the simulation results of its directivity respectively.

FIG. 7 is a configuration diagram which shows the increase in the signalto noise ratio (S/N) as a result of the directionality improvement dueto the coupling of the conical horn antenna.

FIG. 8 a configuration diagram which shows the decrease in the powerconsumption by reducing the size of the image detector, consequentlylowering the thermal mass and thermal time constant.

FIGS. 9 a-9 h and 10 a-10 f show the manufacturing process diagram ofthe image detector coupled with three dimensional conical horn antennaaccording to the present invention.

DESCRIPTION OF THE NUMERIC ON THE MAIN PARTS OF THE DRAWINGS

-   -   10: Substrate    -   20: Horn Antenna Structure    -   25: Waveguide    -   30 a, 30 b: Supports    -   40: Image Detector    -   50: Absorption Layer    -   60: Thermal Isolation Leg    -   100: Substrate    -   102: Sacrificial Oxide Layer    -   104, 108, 112, 116, 120, 124, 128: Etching Mask    -   106: First Silicon Nitride Layer    -   110: Vanadium Oxide Layer    -   114: Conductive Layer    -   118: Second Silicon Nitride Layer    -   122: Third Silicon Nitride Layer    -   126: Side Wall Space

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

From FIG. 2 to FIG. 4 represent the basic configuration diagram, singleisolated configuration diagram and a cross section of the image detectorcoupled with conical horn antenna array according to the presentinvention.

As shown in FIG. 2, FIG. 3 and FIG. 4, the conical horn antennastructure 20 is supported by the supports 30 a, 30 b on the substrate 10and the waveguide 25 of the conical horn antenna is formed at the centerof the conical horn antenna structure 20. The image detector 40 isformed at the lower section of the waveguide 25 and the image detector40 comprises an absorption layer 50 whose diameter is identical to thatof a bottom cross section of the waveguide 25. The image detector 40also includes a circular shaped thermal isolation leg 60, which spans agreater distance than the diameter of the horn antenna wave guide 25,and is formed on the surface of the image detector 40.

The supports 30 a, 30 b prevent the absorption layer 50 of the imagedetector from any damages due to its floatation above the substrate 10at the time of coupling between the image detector 40 and the conicalhorn antenna. Also, in order to maximize the coupling efficiency betweenthe conical horn antenna and the image detector 40, the diameter of thewaveguide of the conical horn antenna coincides with the diameter of theabsorption layer 30.

The thermal isolation leg 60, which is formed in a circular shape on thesurface of the image detector 40 so it reduces the thermal conductivityand improves the sensitivity of the image detector 40.

In FIG. 5 a and FIG. 5 b show an overall configuration of the conicalhorn antenna and the simulation results of its directivity respectively.FIG. 6 a and FIG. 6 b show an overall configuration of the square hornantenna and the simulation results of its directivity respectively.

From the comparison of the directionality between the conical hornantenna and the square horn antenna, it can be seen that thedirectionality of the conical horn antenna is superior than the squarehorn antenna.

FIG. 7 is a configuration diagram which shows the increase in the signalto noise ratio (S/N) as a result of the directionality improvement dueto the coupling of the conical horn antenna. FIG. 8 a configurationdiagram which shows the decrease in the power consumption by reducingthe size of the image detector, consequently lowering the thermal massand thermal time constant.

FIG. 9 a and FIG. 10 f show the manufacturing process diagram of theimage detector coupled with three dimensional conical horn antennaaccording to the present invention.

According to FIG. 9 a and FIG. 9 b, the pattern for the sacrificiallayer 102 is formed by performing a patterning process using the etchingmask 104 so as to form the thermal isolation leg 60 of the imagedetector 40 after depositing a polyimide layer with a thickness 2.0-2.5μm as a sacrificial layer on the substrate 100.

In this case, the pattern size of the sacrificial layer 102 is identicalto the external diameter of the thermal isolation leg 60 of the imagedetector.

According to FIG. 9 c and FIG. 9 d, the pattern for the first siliconnitride layer 106 is formed by performing a patterning process using theetching mask 108 after depositing the first silicon nitride layer 106(Si3N4) on the whole surface of the above resulting product.

According to FIG. 9 e and FIG. 9 f, the pattern for the vanadium oxidelayer 110 is formed by performing a patterning process using the etchingmask 112 after depositing the vanadium oxide layer 110 (VOx) on thewhole surface of the above resulting product in order to form theabsorption layer 50 of the image detector 40.

In this case, the pattern size of the vanadium oxide layer 110 isidentical to the diameter of the absorption layer 50 of the imagedetector 40.

According to FIG. 9 g and FIG. 9 h, the pattern for the conductive layer114 is formed by performing a patterning process using the etching mask116 after depositing a Chrome layer (Cr) as the conductive layer 114 onthe whole surface of the above resulting product.

In this case, only the region around the conductive layer 114corresponding to the absorption layer 50 of the image detector 40 isremoved by etching.

According to FIG. 10 a and FIG. 10 b, the pattern for the second siliconnitride layer 118 is formed by performing a patterning process using theetching mask 120 after depositing the second silicon nitride layer 118(Si3N4) on the whole surface of the above resulting product.

According to FIG. 10 c and FIG. 10 d, the pattern for the side wallspace 126 is formed by performing a patterning process using the etchingmask 124 after depositing the third silicon nitride layer 122 (Si3N4) onthe whole surface of the above resulting product in order to form a sidewall space.

According to FIG. 10 e and FIG. 10 f, the final three dimensionalconical horn antenna coupled image detector is completed by constructinga structure that can be aligned using the negative type photoresistetching mask 128 after removing the sacrificial layer 102 from the aboveresulting product.

As illustrated in FIG. 3, the three dimensional conical horn antennacoupled image detector is finally manufactured.

The advantages of the three dimensional conical horn antenna coupledimage detector according to the present invention are as follows;

Firstly, the crosstalk between the pixels in the array can be reducedthrough an improvement in directionality by coupling the image detectorwith three dimensional conical horn antenna with a superiordirectionality. Also, the circular waveguide improves the value of S/Nratio by acting as a high pass filter.

Secondly, the power consumption can be reduced through a reduction inthe size of the image detector and it can also be used as a high speedimage detector due to its low thermal mass and thermal time constantvalue.

Thirdly, the sensitivity can be improved by lowering the conductivityvalue through the construction of circular shaped thermal isolation legsrather than a linear type with respect to the construction of thermalisolation of the image detector.

1. A three dimensional conical horn antenna coupled image detectorcomprising: a plurality of supports for supporting a horn antennastructure on the upper section of a substrate; a horn antenna waveguideformed at the center of said horn antenna structure; an image detectorat the lower section of said horn antenna wave guide; an absorptionlayer in said image detector which has an identical diameter to that ofa bottom cross section of said horn antenna waveguide; and a thermalisolation leg in said image detector, which spans a greater distancethan the diameter of said horn antenna wave guide.
 2. The image detectoras claimed in claim 1, wherein said thermal isolation leg is configuredto have a circular shape in order to be capable of increasing the lengthof the leg.